1. Field of the Invention
The present invention relates to a fuel tank apparatus for use in a vehicle, and more particularly to an improved fuel tank apparatus for use in a vehicle which is constituted such that evaporated fuel within a fuel tank can be restrained from flowing out into the atmosphere through a filler tube upon filling fuel into the fuel tank.
2. Description of the Prior Art
A known fuel tank apparatus for a vehicle such as an automobile is for example illustrated in FIG. 1. As shown in FIG. 1, the known fuel tank apparatus comprises a fuel tank 1 for storing fuel therein. A filler tube 2 for introducing fuel into the fuel tank 1 is connected at one end thereof to the fuel tank 1. An inlet port is provided at the other end of the filler tube 2. A filler cap 3 is removably attached to the other end of the filler tube 2 so as to be able to close the inlet port thereof. A vent tube 4 for venting gas within the fuel tank 1 when the fuel is introduced into the fuel tank 1 is connected between the fuel tank 1 and the filler tube 2. Namely, one end of the vent tube 4 is connected to the upper portion of the fuel tank 1 and the other end thereof is connected to the filler tube 2 in the vicinity of the inlet port thereof. A canister for absorbing and then treating evaporated fuel generated in the fuel tank 1 is connected to the fuel tank through an evaporation tube 6 which is also connected at one end thereof to the upper portion of the fuel tank 1. A check valve 7 is provided in the evaporation tube 6. The check valve 7 is adapted to open to release the evaporated fuel from the fuel tank 1 to the canister 5 when pressure inside the fuel tank 1 exceeds a predetermined level due to evaporation of the fuel in the fuel tank 1.
An apparatus similar to the above-described apparatus is for example disclosed in Japanese Laid-open Patent Publication No. SHO 61-191427.
According to the known fuel tank apparatus as described above, it is possible to maintain the pressure inside the fuel tank 1 constant in the cases where the vehicle is not only running and but also standing, and restrain the evaporated fuel from flowing out into the atmosphere. That is, even if the pressure inside the fuel tank 1 is increased due to evaporation of the fuel in the fuel tank 1, the check valve 7 is opened so that the evaporated fuel within the fuel tank 1 is released into the canister 5 through the evaporation tube 6. The evaporated fuel which has been introduced into the canister 5 is then absorbed and treated therein, thereby enabling to prevent air pollution from being caused by flowout of the evaporated fuel.
On the other hand, however, the known fuel tank apparatus has the following problem. Namely, if the pressure inside the fuel tank 1 is less than the predetermined level but higher than the atmospheric pressure, the check valve is not operated and therefore the evaporated fuel still remains in the fuel tank. In this case, there is a possibility that the remaining evaporated fuel in the fuel tank 1 flows out to the atmosphere from the inlet port of the filler tube 2 when the filler cap 8 is removed upon filling fuel into the fuel tank 1. This problem may be overcome by setting the predetermined level as low as possible. However, this leads to the difficulties in adjustment of the check valve and design